With Horizon NDR, the issue is moot - you don't need a management server so no SIC.
Step 1: Install gateway with R81.10 or R81.20, latest jumbo.
Step 2: Define a sensor object on Horizon NDR, GENERATE REGISTRATION KEY, and run the provided command on your gateway.
Step 3: Attach the gateway to a customer's SPAN port, and wait for logs to accumulate.
Step 4: On the REPORTS tab, click "+ REQUEST", select report type, and submit. After a few minutes you'll get your report.
Step 5: Move the gateway to another customer's site, and repeat from Step 3.
Note: It's best if you provision a separate NDR subdomain for each customer, so that the reports don't contain residual information from the previous one.